(a) Field of the Invention
The present invention relates to a positive active material for rechargeable lithium batteries and a method of preparing the same and, more particularly, to a manganese-based positive active material for rechargeable lithium batteries which has a good cycle life characteristic.
(b) Description of the Related Art
Generally, manganese-based compounds such as LiMn.sub.2 O.sub.4 and LiMnO.sub.2 are the positive active material of choice for rechargeable lithium batteries because of their low cost, abundance and environmentally friendly characteristics. Among such manganese-based compounds, LiMn.sub.2 O.sub.4 is particularly stable for the battery use and thus attractive for the electric vehicle application.
However, as compared to other lithiated transition metal oxides such as LiCoO.sub.2 and LiNiO.sub.2, LiMn.sub.2 O.sub.4 has a relatively low discharge capacity. Furthermore, when high rate of charge and discharge operations are cycled, the discharge capacity is excessively reduced. In particular, when the charge and discharge operations are continuously performed at high temperatures, manganese distributed in the surface of LiMn.sub.2 O.sub.4 readily elutes to the electrolyte, causing a disproportionation reaction. This reaction seriously deteriorates the cycle life characteristic of the battery.